Exercise device



FIG. 1 is a elevation view of an exercise device showing my new design;

FIG. 2 is a top plan view thereof, wherein the bottom plan view is identical; and,

FIG. 3 is a side view thereof, wherein the opposite side is identical.

The dashed lines in FIG. 1 depict stitching. 

The ornamental design for an exercise device, as shown and described. 